Quarkonium results in pp collisions from ALICE

Transcription

1 Quarkonium results in pp collisions from ALICE Giuseppe E Bruno Università di Bari and INFN Italy for the ALICE collaboration Outline: introduction measurements in pp at s=7 and 2.76 TeV Integrated and differential cross sections for inclusive production Quarkonia in Multiplicity dependence at s = 7 TeV Deconfined Matter J/ψ from B decays at s = 7 TeV outlook J/ψ polarisation and Upsilon measurements Acitrezza at s = 7 TeV September

2 Introduction do I need to motivate the study of quarkonia within this audience? J/ψ is puzzling in PbPb and in fact we are at work at this meeting but J/ψ production is not that obvious in p-p collisions too the production mechanisms in p-p collisions are not fully understood but recent theoretical developments can account for the yields J.P.Lansberg, PoS(ICHEP 2010), 206 Quarkonia in deconfined matter Giuseppe E. Bruno 2

3 Introduction S.J.Brodsky, J.P.Lansberg, PRD81 (2010) theoretical uncertainties are big NNLO* corrections in the CSM model give a good description of the p t spectrum at intermediate p t. more observables from experiment should be employed to constrain theory? Quarkonia in deconfined matter Giuseppe E. Bruno 3

4 Introduction Experimentally accessible information production rates (cross-sections) inclusive and exclusive channels: direct, feed-down from beauty and higher charmonium states differential vs. rapidity, transverse momentum correlations J/ψ correlations with hadrons, leptons, photons understand the production context event multiplicity underlying event, jet fragmentation cone polarization measurements Quarkonia in deconfined matter Giuseppe E. Bruno 4

5 Quarkonia with ALICE e+ e- µ + µ - Quarkonia can be measured in two ways: in the central barrel in the e+e- channel ( y <0.9) in the forward spectrometer in the µ+µ- channel (2.5<y<4) Quarkonia in deconfined matter Giuseppe E. Bruno 5

6 Quarkonia at central rapidity Key detectors: tracking TPC,ITS PID TPC, TOF, TRD, EMCAL vertexing ITS trigger EMCAL, TRD EMCAL Quarkonia in deconfined matter Giuseppe E. Bruno 6 TRD PHOS ITS TPC TOF e + e - 0<φ<2π η e < 0.9 HMPID L3 Magn

7 Quarkonia at central rapidity tracking PID K. Aamodt et al. (ALICE Collaboration), Phys. Lett. B in press, arxiv: Quarkonia in deconfined matter Giuseppe E. Bruno 7

8 Quarkonia at forward rapidity 0<φ<2π -4.0<η µ <-2.5 p µ > 4 GeV/c coverage: -4.0<η<-2.5 and p µ >4.0 GeV/c dipole magnet and 5 tracking chambers used for momentum measurement muons are isolated using hadron absorbers it can run at higher luminosities compared to the slower central rapidity detectors allows measurement of heavy quarkonia (J/ψ, ψ', Υ family) Quarkonia in deconfined matter Giuseppe E. Bruno 8

9 Event selection and data sample Triggers: Minimum bias (MB) based on interaction trigger: SPD(pixels) or V0-A(scintillators) or V0-C(scintillators) At least one charged particle in 8 η units 87% efficient on σ inel V0-C SPD Single muon trigger (p thr T =0.5 GeV/c): Forward Muon in coincidence with MB read out MUON, SPD, ZDC, V0, FMD V0-A Results presented today based on: 2010 pp run at 7 TeV 2011 pp run at 2.76 TeV Energy J/ψµ + µ - J/ψe + e TeV 15.6 nb nb TeV 20.2 nb nb -1 Quarkonia in deconfined matter Giuseppe E. Bruno 9

10 Kinematical and track quality cuts J/ψ e + + e - η e < 0.9 p Te > 1.0 GeV/c y J/ψ <0.9 high quality ITS+TPC tracks electron PID based on TPC's de/dx rejection of e from γ conversions J/ψ µ + + µ - p µ > 4.0 GeV/c 2.5<y J/ψ <4.0 one muon trigger matching 17.6<R abs <89 cm (radial track position at the end of the absorber) Quarkonia in deconfined matter Giuseppe E. Bruno 10

11 Efficiency times acceptance J/ψ e + e - at 7 TeV, y < 0.9 J/ψ µ + µ - at 2.76 TeV, 2.5<y <4 Acceptance x efficiency <Axε>=10% <Axε>=33% ALICE unique measurement at LHC Quarkonia in deconfined matter Giuseppe E. Bruno 11

12 Signal extraction (7 TeV) 2 Counts per 40 MeV/c 180 OS 160 LS* TrkRot ALICE pp s=7 TeV L int =5.6 nb -1 N J/ψ =352±32 S/B=1.2 S/ (S+B)=14 K. Aamodt et al. (ALICE Collaboration), Phys. Lett. B in press, arxiv: OS-1.23*LS MC ( 2 /dof=1.2) m ee 2 (GeV/c ) signal extracted using bin counting, after bkg. subtraction MC simulations describes well the signal shape Quarkonia in deconfined matter Giuseppe E. Bruno 12 L int =7.9 nb -1 N J/ψ =957±56 S/B 2.6 m J/ψ =3.118±0.005 GeV/c 2 σ J /ψ =94±8 MeV/c 2 Fit with Crystall-Ball functions (J/ψ and ψ ) plus double exponential (bkg.) describes well the dimuon invariant mass spectra

13 Signal extraction (2.76 TeV) N J/ψ =1287±48 L int =1.1 nb -1 N J/ψ =41±9 signal extracted using bin counting, after bkg. subtraction MC simulations describes well the signal shape Quarkonia in deconfined matter Giuseppe E. Bruno 13 Fit with Crystall-Ball functions (J/ψ and ψ ) plus double exponential (bkg.) describes well the dimuon invariant mass spectra

14 Systematic uncertainties at s=7 TeV e + e - µ + µ - Signal extraction 8.5% 7.5% Acceptance input 1.5% 5% Trigger efficiency 0 4% Reconstruction efficiency 11% 3% Trigger enhancement - 3% Luminosity 4% 5.5% B.R. 1% Polarization λ=-1 λ=1 λ=-1 λ=1 Collins-Soper +19% -13% +31% -15% Helicity +21% -15% +22% -10% systematic error due to the unknown polarization estimated for extreme scenarios major systematic errors come from signal extraction and reconstruction efficiency (for the di-electron channel) similar uncertainties at s=2.76 TeV Quarkonia in deconfined matter Giuseppe E. Bruno 14

15 Rapidity dependence of the inclusive cross-section d! (pp! J /" + X) dy = corr N J/"! MB "y BR(J /"! l + l # ) N MB Cross section determination from van der Meer scan: K. Oyama et al. (ALICE Collaboration) arxiv: TeV σ MB = 62.3±4.3 mb 2.76 TeV σ MB = 54.2±3.8 mb systematic uncertainties from beam intensities (~4%) 7 TeV ALICE coll., PLB in press arxiv: (2011) 2.76 TeV ALICE preliminary +1.6! J/" ( y < 0.9) =10.7±1.0(stat)±1.6(syst) (syst pol) µb! ! J/" (2.5 < y < 4) = 6.31± 0.25(stat)± 0.76(syst) (syst pol) µb! ! J/" ( y < 0.9) = 6.44 ±1.42(stat)± 0.88(syst)± 0.52(lumi) (syst pol) µb! ! J/" (2.5 < y < 4) = 3.46 ± 0.13(stat)± 0.32(syst)± 0.28(lumi) (syst pol) µb!1.11 Quarkonia in deconfined matter Giuseppe E. Bruno 15

16 Rapidity dependence of the inclusive cross-section Error bars are statistical and systematic errors (added in quadrature), excluding luminosity and polarization Boxes are correlated error bars from luminosity Comparison to CMS and LHCb shows agreement within error bars 1 open: reflected ALICE: Phys. Lett. B in press ATLAS: Nucl. Phys. B850 (2011) 387 CMS Phys. J. C71, (2011) 1575 LHCb Eur. Phys. J. C71 (2011) 1645 Quarkonia in deconfined matter Giuseppe E. Bruno 16 /dy (µb) d J/ ALICE, e e ALICE, µ + µ - CMS LHCb pp s=7 TeV y

17 p T dependence of the inclusive cross-section Error bars are statistical and systematic errors (added in quadrature), excluding luminosity and polarization Boxes are correlated error bars from luminosity Good agreement between ALICE and LHCb for 2.5<y<4.0 At mid-rapidity, ALICE and CMS+ATLAS cover the full p t range ALICE: Phys. Lett. B in press ATLAS: Nucl. Phys. B850 (2011) 387 CMS Phys. J. C71, (2011) 1575 LHCb Eur. Phys. J. C71 (2011) 1645 Quarkonia in deconfined matter Giuseppe E. Bruno 17 dy (µb/gev/c) T /dp J/ 2 d ALICE e e, y <0.9 - ALICE µ + µ, 2.5<y<4.0 CMS, y <1.2 ATLAS, y <0.75 LHCb, 2.5<y<4.0 pp s=7 TeV p T (GeV/c)

18 Comparisons to theoretical predictions Inclusive J/ψ production at LHC energies, at low pt: J/ψ feed-down from higher charmonium states χ c and ψ ~ 40% J/ψ from B-hadrons ~ 10% direct J/ψ ~ 50% CS+CO NLO (NRQCD) reproduces well the spectra for p T > 3 GeV/c CS LO for direct J/ψ production reproduces rapidity dependence, despite large uncertainties Quarkonia in deconfined matter Giuseppe E. Bruno 18

19 Energy dependence CDF Collaboration PRD71 (2005) PHENIX Collaboration, PRL 98 (2007) M.Mangano et al., Nucl.Phys.B373 (1992) 295 line = NLO cross section calculation for ccbar scaled to CDF data J/ψ mean p T grows roughly as ln(s 1/2 ) Quarkonia in deconfined matter Giuseppe E. Bruno 19

20 Multiplicity dependence Charged particle multiplicity (dn ch /dη max ~30) reached in pp at 7 TeV is comparable with semi-central CuCu collisions 200 GeV heavy-ion like effects in p-p collisions at high multiplicity at LHC? Almost linear increase of J/ψ yield with charged particle multiplicity Multi-parton interactions? Contributions from higher order pqcd diagrams? Different increase with respect to high p T muons (~80% from heavy flavour decays at 4 <p T < 8 GeV/c) Quarkonia in deconfined matter Giuseppe E. Bruno 20

21 Prompt J/ψ and J/ψ from B hadrons Component of J/ψ from B hadrons can be measured thanks to the excellent vertexing capabilities of the ITS technique: simultaneous likelihood fit of invariant mass and pseudo-proper decay length l J/ψ y J/ψ <0.9 l m L pt r ( sec r prim = J / ψ xy L xy = J / ψ ( J / ψ ) rϕ) Quarkonia in deconfined matter Giuseppe E. Bruno 21

22 Fraction of J/ψ from B lowest p T at central rapidity at LHC energies nicely complement the ATLAS and CMS measurements at y=0 Quarkonia in deconfined matter Giuseppe E. Bruno 22

23 Prompt and non-prompt J/ψ cross section, p t >2 GeV/c inclusive cross-section, p t >2 GeV/c: ( ) dy d! inclusive p T J/" > 2GeV / c, y J/" < 0.9 fraction of J/ψ from B hadrons: F B p T J/! > 2GeV / c, y J/! < 0.9 ±4%(lumi) = 3.76 ± 0.37(stat)± 0.49(syst) (pol.) µb!0.59!0.022(! ( ) = ± ± 0.026(syst) CS =!1) (!HE =+1) prompt cross-section, p t >2 GeV/c: d! prompt ( p J/" T > 2GeV c, y J/" < 0.9) dy!0.29(! CS = +1) (! CS =!1) = 3.20 ± 0.38(stat)± 0.43(syst)!0.58(!HE = +1) (! HE =!1) µb ±4%(lumi) Quarkonia in deconfined matter Giuseppe E. Bruno 23

24 Outlook: J/ψ polarisation (2.5<y<4) key observable to study the production mechanism determination of the full angular dependence of J/ψ (λ θ, λ φ, λ θφ ) is ongoing preliminary results soon: expected error on λ θ ~ 0.15 for 3<p T <8 GeV/c Quarkonia in deconfined matter Giuseppe E. Bruno 24

25 Outlook: upsilon family and more 2011 data will allow the measurement of Υ in the di-muon channel upsilon data now on tape and results will be available soon 2011 and beyond: extension of PID and trigger to EMCAL and TRD Υ family measurements at both rapidities; J/ψ-hadron correlations and radiative decay from higher charmonium states (χ c and ψ ) at mid-rapidity. Quarkonia in deconfined matter Giuseppe E. Bruno 25

26 Conclusions J/ψ production in p+p collisions at s = 2.76 and 7 TeV: integrated and differential cross sections for inclusive production were presented. Results have been compared to other experiments, as well as to theoretical models on quarkonia production results at 2.76 TeV serve also as reference to our PbPb measurements linear dependence on charged particle multiplicity was observed the fraction of J/ψ from B decays was measured at mid-rapidity polarization analysis almost ready, results soon upsilon measurement with 2011 data coming Quarkonia in deconfined matter Giuseppe E. Bruno 26

27 Afterword you may wonder what is the picture in my first slide dn/dm J/ψ Υ ψ M inv (l +,l - ) Quarkonia in deconfined matter Giuseppe E. Bruno 27

28 Afterword from the movie La terra trema by Luchino Visconti, based on the novel by Giovanni Verga I Malavoglia set in Acitrezza Quarkonia in deconfined matter Giuseppe E. Bruno 28

29 Afterword dn/dm J/ψ ψ Υ M inv (l +,l - ) thanks for your patience Quarkonia in deconfined matter Giuseppe E. Bruno 29